The sum of two angles is $77^\circ$. Angle 2 is $99^\circ$ smaller than $3$ times angle 1. What are the measures of the two angles in degrees?
Answer: Let $x$ equal the measure of angle 1 and $y$ equal the measure of angle 2. The system of equations is then: ${x+y = 77}$ ${y = 3x-99}$ Since we already have solved for $y$ in terms of $x$ , we can use substitution to solve for $x$ and $y$ Substitute ${3x-99}$ for $y$ in the first equation. ${x + }{(3x-99)}{= 77}$ Simplify and solve for $x$ $ x+3x - 99 = 77 $ $ 4x-99 = 77 $ $ 4x = 176 $ $ x = \dfrac{176}{4} $ ${x = 44}$ Now that you know ${x = 44}$ , plug it back into $ {y = 3x-99}$ to find $y$ ${y = 3}{(44)}{ - 99}$ $y = 132 - 99$ ${y = 33}$ You can also plug ${x = 44}$ into $ {x+y = 77}$ and get the same answer for $y$ ${(44)}{ + y = 77}$ ${y = 33}$ The measure of angle 1 is $44^\circ$ and the measure of angle 2 is $33^\circ$.